Radford, EP 0122985 entitled “Improvements Relating to Footwear” discloses a sole unit molded from a resilient material, in which sole unit is provided a plurality of cavities and a system of channels formed in the upper surface of the sole unit which interconnect the cavities. At the lower end of each cavity a bulge extends downwardly from the bottom surface of the sole unit at the location of each cavity, so that the pressure exerted by the foot on any bulge expels air from the associated cavity, and the action of walking pumps air from one cavity to another along the channels and in this way absorbs the shocks of impact of the foot with the ground. The cavities are formed substantially wholly in the general thickness of the sole unit.